This is simple physics, and many tronners haven't taken the time to think about this.
If you are closer to the rim, you are much harder to trap and have an overall advantage at trapping your opponent. This effect is most easily demonstrated in a 1v1, while less effective when there are lots of people.
Stay away from the center at all costs because you can be trapped from any direction, but if you are closer to the rim, you can only be trapped from in front. Also, you have much more influence on your opponent if you take this position, while they can hardily affect you.
This isn't saying that you should rim, just take a spot closer to the rim than anyone else (sort of like boxing them in). But this also shows why people hate rimmers so much, because they are much harder to kill than normal.
Advice is to always take the spot closer to the rim than anyone else. If you get caught on the center (even while trapping), your should move towards the rim so you can gain or maintain advantage.
While the mechanics of this are extremely hard to explain, it is nonetheless very useful.
Hopefully these animations can prove at least some part of it.